1. Field of the Invention
This invention relates to an air-conditioning control method for controlling the air-conditioning of the inside of a vehicle such as a passenger car, which can continue control of air-conditioning making use of outputs from other normal detection sensors without using a specific detection sensor.
2. Description of the Prior Art
For automatic control of the air-conditioning of the inside of a vehicle, output signals from detection sensors for detecting various environmental factors, such as an output signal from an inside temperature detection sensor, an output signal from an outside temperature detection sensor, a detection signal from an outlet temperature detection sensor of an air-conditioner, an output signal from a direct solar radiation sensor for detecting a heating value of solar radiation and an output signal from a car body temperature detection sensor, are important data for controlling the air-conditioner. When a certain detection sensor goes wrong, the size of an environmental factor corresponding to the malfunctioning detection sensor is calculated from a heat balance calculation model for each environmental factor to obtain an estimated value.
If control of the air-conditioner is continued based on this estimated value and output values from the other normal detection sensors, the sac status of control as that of air-conditioning control before the failure can be obtained even during the period until the malfunctioning detection sensor is fixed. This prior art is disclosed in JP-A-5-116522 and JP-A-5-50836 (the term "JP-A" used herein means "unexamined published patent application"). However, JP-A-5-50836 has the defect that a car body temperature can be estimated but an outside temperature cannot be estimated.
Further, JP-A-5-116522 teaches that the difference between a preset target inside temperature and an inside temperature obtained from an inside temperature detection sensor is integrated by a time to obtain a correction value for an outside temperature. This correction value is added to the estimated outside temperature to approximate the estimated outside temperature to a more accurate outside temperature. However, even this method still cannot theoretically guarantee convergence into a correct outside temperature.
However, there is a limit to types of detection sensors whose output values can be estimated. Since an estimated output value from a malfunctioning detection sensor is not a highly accurate estimated value, there is a fear that control of the air-conditioner may be deviated from normal control and there is the possibility that passengers are forced to be in an unpleasant car environment.